Development of metazoans requires the production of multiple cell types and the morphogenesis of complex multicellular structures. Genetic studies have established roles for glycosylation and proteoglycan biosynthesis in developmental signaling. The nematode Caenorhabditis elegans is a good model system to study the role of glycoconjugates in multicellular organisms as well as a prototypic model for parasitic nematodes because of the knowledge of its complete genomic sequence and development. In this R2 I (Exploratory / Developmental) grant application, we wish to explore a novel potential functional linkage between expression of glycoconjugates and developmental events in C. elegans. Srf-9, srf-8 and srf-4 (surface) are single loci mutants that have multiple defects, including uncoordinated movement, protruding vulva, abnormal egg laying, and defective copulatory bursae and gonad morphology, yet they were isolated based on their ectopic surface binding to a lectin which binds to N-acetylglucosamine. Mutations in srf-9, srf-8 and srf-4 interact with mutations in the lin-12 gene, which a member of the LIN- 1 2/NOTCH family of receptor proteins that mediate cell-cell interactions to specify cell fate during development. We will test the hypothesis that the srf-9, srf-8 and srf-4 genes are involved in the biosynthesis, post-translational processing or secretion of glycoconjugates, and therefore link developmental events with glycoconjugates expression. Specifically, the proposed work will: 1) Define the glycoconjugates affected in srf-9, srf-8 and srf-4 mutants, through the structural characterization of cuticle glycan fractions, 2) Identify the srf-9, srf-8 and srf-4 genes through molecular cloning using a combination of Single Nucleotide Polymorphism (SNP) mapping, and marker rescue experiments. The information derived from these studies will provide the tools to study the role of these genes in developmental events in the nematode C. elegans. Because complex phenotypes are the hallmark of several human genetic disorders, including some that affect glycosylation, the proposed studies will establish the feasibility of using C. elegans srf mutants as a model for glycosylation disorders in humans.